The use of access doors in known in the prior art. These doors are often mounted within the ground and control access to underground utilities. Access doors have to be strong enough to prevent unauthorized access as well as to withstand vehicle traffic. But access doors must also be light enough to permit opening by a single user. Access door must also be capable of opening wide enough to ingress of larger equipment.
An example of a prior art access door is disclosed in U.S. Pat. No. 4,133,074 to Schack. Schack discloses a spring assisted door construction. The door of Schack includes both closed, raised, and fully open positions. A first pair of torsion rods are arranged to be loaded when the door is swung down to a closed position from a raised position. A second pair of torsion bars are arranged to be stressed when the door is swung down to its fully open position from its raised position.
Although Schack addresses issues associated with the weight of the door via torsion bars, it nonetheless does not provide a door with discrete opened orientations. Nor does Schack otherwise relate to mechanism for locking an access door in one of two opened positions.